EndUserSignature

A signature the client produced with a credential it already holds, together with everything the
provider needs to verify it. Which shape arrives depends on the mechanism behind the credential,
not on the ceremony being confirmed: a passkey and a key pair prove themselves differently.

{
    "kind": "webAuthn",
    "credentialId": "string",
    "clientData": "string",
    "signature": "string",
    "authenticatorData": "string"
}